Natural pearls are pearls found in the wild. Until Japanese succeeded in cultivating artificial pearls in the early 20th century, natural pearls were used by many royals and nobles for thousands of years.
They were mostly collected in the Persian Gulf and sold to nearby countries and even Europe, and India. That's why, in some Middle Eastern countries, natural pearls were once as important to the country's economy as oil is now. People like Ibrahim Al Fardan from the UAE were really successful in this business, and his families still own extremely expensive collections of natural pearl jewelry.
However, after people learned how to farm pearls, the pearl industry changed completely. Now, natural pearls are seen only sometimes in museums or auctions like Sotheby's. Also more people can buy pearls, thanks to the lower prices.